I know I've seen several of the suits used by Firefly at one of the prop parties held at Global Effects in LA. They specialize in space suits, both historical and Sci-Fi versions used in From the Earth to the Moon, Apollo 13, Armageddon, The Core, etc.
The space suits that Mal and Zoe wear are originally from Soldier with Kurt Russell. You can even see where the "Amercian Forces / Fuerzas Americana" patches were previously mounted and then removed for Firefly / Serenity.
I know I've seen several of the suits used by Firefly at one of the prop parties held at Global Effects in LA. They specialize in space suits, both historical and Sci-Fi versions used in From the Earth to the Moon, Apollo 13, Armageddon, The Core, etc.
The original helmet from Soldier is actually the helmet that Jayne wears with his yellow space suit. Mal and Zoe have differently fitting helmets, which make the original helmets seals look like some sort of collar.